1. Field of the Invention
The invention relates to a method and apparatus for extracting heat and mechanical energy from a pressured gas by expanding same in a rotating fluid pressure chamber containing a free piston.
2. Description of the Prior Art
In my above identified co-pending applications, which do not constitute prior art, there are disclosed a variety of forms of centrifugal piston expanders. Such disclosed expanders comprise a rotating body upon which one or more cylinders are mounted for co-rotation. Each cylinder defines a fluid pressure chamber extending from a point remote from the axis of rotation of the rotating body to a point proximate to the axis of rotation. The longitudinal axis of the fluid pressure chamber may be linear or arcuate but, in any event, no substantial portion of the longitudinal axis is radially disposed with respect to the rotational axis.
A free piston is mounted within the cylinder for sliding sealable movements through the pressure chamber. Inlet valves are respectively provided in the outermost ends of the cylinders through which charges of a pressured gas may be introduced into the fluid pressure chambers, which results in driving the pistons radially inwardly toward the axis of rotation by expansion of the pressured gas. The reaction force of the gas on the outermost end of the cylinder produces a torque to assist in the rotation of the rotating body. A motor is employed for use as required to obtain a speed of rotation sufficient to insure the return of the free pistons to the outermost ends of the fluid pressure chambers due to the action of centrifugal force. Said motor may also function as a generator, as known to those skilled in the art. Exhaust valves in the outer ends of the cylinders open during the return movement of the free pistons to supply the cooled, expanded gas to a heat exchanger, or, if the gas is air, to a room.
In an attempt to optimize the performance of these types of centrifugal piston expanders, a computer analysis was undertaken to permit calculation of torque output and piston speed as a function of the diameter and longitudinal length of the fluid pressure chamber, rate of rotation of the cylinder, the weight of the piston, the pressure of the gas supplied to the pressure chamber and the time of application. Such computer analysis surprisingly indicated that for some combinations of the aforementioned variables, the centrifugal force acting on the piston was insufficient to arrest the inward movement of the piston, with the result that it would slam into the inner end wall or stop ring of its cylinder which, of course, is an undesirable condition.